The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.
A composite wheel generally includes two main sections, a rim portion and a face portion. The rim portion comprises an annulus structure configured to receive and seat a tyre. The face portion includes a hub which is used to fix the wheel to the vehicle, and a connection structure such as a series of spokes or a disc which extends between and interconnects the hub and the rim. Lateral, vertical and torsional loads are transmitted through the tyre to the rim portion of the wheel which then produce bending and torsional stresses in the connection structure.
The Applicant has produced a one-piece composite wheel, which is described, for example, in International Patent Publication WO2010/024495A1. The creation of a one-piece composite wheel generally necessitates use of a separate rim portion mold and associated reinforcement and face portion mold and associated reinforcement. The separate rim and face mold portions are then interconnected in a final molding process which allows the overall composite wheel to be integrally formed. A stiff, strong connection between the rim portion and the face portion, in particular the connection between the spokes and the rim, is required to provide a mechanically efficient structure having stiffness and strength and also efficiently transmit loads generated between the tyre and road, through the rim and spokes.
Previous proposed connections between the rim portion and the face portion structures of composite wheels have used a bolted connection or an adhesive bond to interconnect the connection structure and rim. However, these forms of connection can add significant mass to the wheel, require joining structures which can provide stress points in the wheel structure and configuration, and/or can form a weak bond between the adjoining portions of the wheel. The Applicant is aware that a number of these types of connections have been the subject of mechanical failure when tested under normal road conditions.
It would therefore be desirable to provide an improved or alternate connection between the rim portion and the face portion of a composite wheel.